The following terminology is used in this text. The expression “kinematic state of a physical component” refers to the position, and/or velocity, and/or acceleration of the physical component with respect to some pre-determined reference system. The expression “relative kinematic state of two physical components” refers to the position, and/or velocity and/or acceleration of the physical components relative to each other. The expression “kinematic quantity” is used in this text to refer to a physical quantity representative of the kinematic state.
The relative kinematic state of two physical components can be measured using any of a variety of sensing techniques. An example of a known sensing technique is based on determining the strength of a magnetic field, or a rate of change in the magnetic field strength, as a representative of relative position or of relative velocity of a first physical component relative to a second physical component. Magnetic sensing is an example of a remote sensing technique. That is, it is contactless in that a magnetic sensor arrangement does not introduce any physical contact with the first and second components. As a result, a magnetic sensor arrangement is practically insusceptible to, e.g., the accumulation of dirt on the components, to the presence of lubricants and, if properly designed, to magnetic fields from an external source.
A magnetic sensor typically uses a Hall-effect sensor. A Hall-effect sensor supplies an output voltage, whose magnitude and polarity are representative of the strength and direction of the component of the magnetic field that is orthogonal to the sensor's sensitive part, known as the “Hall plate”.
A magnetic sensor arrangement can be physically integrated with a through-shaft bearing. The sensor arrangement is then used to determine, e.g., the angle of rotation between the inner ring and the outer ring of the bearing. If, for example, the inner ring is kept stationary with respect to a shaft, and the outer ring is kept stationary with respect to a frame supporting the shaft, the sensor supplies an output signal indicative of the rotation angle of the shaft around the shaft's axis relative to the frame.
A class of through-shaft sensor-bearing units, manufactured by SKF, is designed for automotive applications to make steering easier and more precise. Based on existing, proven SKF technology focusing on positioning, rotation angle and speed sensing, these sensors are integrated in a bearing positioned on a shaft, from where they transmit data to a standard electronic controller. The controller monitors the desired level of power that the electric servo-motor needs to deliver in order to assist the driver with steering. The sensors enable more precise power-assist steering, from left-lock all through right-lock for all driving conditions, including highway to parking. For more background information see, for example, the “General Catalogue” of SKF, edition 2005, chapter “Mechatronics”, section “Sensor-Bearing Units”, or U.S. Pat. No. 6,043,643, incorporated herein by reference.
Consider a known example of a through-shaft sensor arrangement integrated with a bearing, and configured for absolute-angle sensing in an automotive steering application. The sensor arrangement comprises a diametrically magnetized bipolar ring. The magnetic field of the ring extends primarily radially in the plane of the ring. The ring is attached to, and turns with, a shaft, whose angular position is to be sensed relative to a stationary component. The sensor arrangement has one or more Hall-effect sensors for sensing the radial component of this magnetic field. The Hall-effect sensors are accommodated at the stationary component. The Hall-effect sensors are positioned around the ring at 90° angular position intervals. The Hall-effect sensors produce output voltages that depend on the magnitudes of the field sensed, which in turn depend on the relative angular position of the bipolar ring relative to the Hall-effect sensors. The output voltages are converted into digital data and subjected to data processing in order to provide an output representative of the angular position of the shaft. The angular position of the shaft and/or its rate of change determine the amount of assistance to be delivered by a servo-motor, possibly in combination with other input quantities such as road speed of the vehicle.
The Hall-effect sensor used is comprised in an electronic device, e.g., with a single-in-line (SIL) package, whose wire leads are soldered to a printed circuit board (PCB). The electronic device accommodating the Hall-effect sensor is of the so-called “through-hole” design, and the wire leads are to be stuck into holes in the PCB before the device can be soldered to the PCB The Hall plate of such a Hall-effect sensor is oriented substantially perpendicular to the PCB.